Hydraulic slicer



April 15, 1952 I G. E. ZWEIFEL ET AL 2,592,782

HYDRAULIC SLICER Filed Jan. 10, 1947 V 5 Sheets-Sheet l Geoggefi'. Zwez'f'el INVENTORS an'awanczld Hfiookhulfz April 1952 G. E. ZWEIFEL ETAL HYDRAULIC SLICER 5 Sheets-Sheet 2 Filed Jan. 10, 1947 INVENTORS Q Geogge E. ZWei e1 cmdfionald H5 Byf April 15, 1952 G. E. ZWElFEL ET AL HYDRAULIC SLICER 5 Sheets-Sheet 3 Filed Jan. 10, 1947 INVENTORS George E. Z wez'fel and Donald HBookhuliz BY v44! April 15, 1952 e. E. ZWEIFEL ET AL 2,592,782

HYDRAULIC SLICER Filed Jan. 10, 1947 5 Sheets-Sheet 5 7k Q I INVENTORS eo gef. Z wez'fel and Donald fifloaklzuli'z 6 Dzls p Zacemenfi 5% LH 1 5 Tzme Patented Apr. 15, 1952 HYDRAULIC SLICER George E. Zweifel and Donald H. Bookhultz, Portland, reg., assignors to George E. Zweifel & Company, Portland, 0reg., a partnership Application January 10, 1947, Serial No. 721,396

8 Claims.

This invention relates to apparatus for cutting wood into thin sheets or veneers. More particularly, the invention pertains to a hydraulically actuated machine for use in slicing a block or chunk of wood to produce veneers suitable for use in the large scale production of plywood.

By far the greatest volume of wood veneer for use in the manufacture of plywood is produced at the present time by peeling down rotating logs in a lathe type of machine. This results in the rapid formation of large sheets of veneer. The veneer so produced is of the slash-grain type, however, which is suitable for use in many applications but not in others principally because of undesirable grain patterns, problems of grainraising, and structural weakness. The method is applicable, furthermore, only to the woods of certain species of trees.

To avoid these difficulties, it also has been common practice, although on a much smaller scale, to make veneers for plywood manufacture by slicing off sheets of veneer from a non-rotating block of wood, commonly referred to as a fiitch. Such practice may be used to produce vertical grain veneers, i. e., veneers in which the out has been made perpendicular to the grain of the wood to give a relatively strong product which has an attractive grain pattern and which is substantially free of grain-raising phenomena.

Thus, in the manufacture of furniture veneers from high quality woods, a fiitch is caused to move against a stationary knife so as to slice off a veneer of a desired thickness, the machine being stopped and the position of the flitch relative to the knife being changed as necessary to accommodate varying grain structures. This procedure obviously is slow, cumbersome and costly. and is not economically suited to the large scale production of structural plywood.

A different type of slicing apparatus has been employed in the manufacture of vertical grain veneers for use in the production of battery plate separators. In this art, the flitch is held stationary while a moving knife slices on the veneers. Mechanical means comprising a crank arm attached to a rotating drive wheel are used to actuate the knife. Certain defects are, however, inherent in the operation of a crank mechanism as applied to the actuation of a knife to be used for cutting wood veneers. Thus, because of the rotating motion of the drive wheel, the velocity of the crank arm and of the knife to which it is attached is greater at the middle than at the end of each stroke or cycle. As a result, the wood is cut at varying rates of speed to produce a veneer having a rough and non-uniform surface. Furthermore, since the velocity of the knife is relatively low at the end of the cutting stroke, the wood fibers acted upon toward the end of each stroke are pulled or torn apart and are not sharply severed to give a clean cut.

Still another disadvantage of the mechanical slicer resides in the fact that the stroke of the knife is fixed by the length of the crank arm. Hence the machine is not adjustable to accommodate fiitches of varyin vertical dimensions without disassembling it and making fundamental mechanical adjustments. On the other hand, if such changes are not made, a large portion of the cuttin stroke is wasted with consequent reduction in production. Nor is the cutting angle or draw of the device adjustable to conform to flitches of varying grain structure. It is necessary when grain structure varies to stop the machine and manually shift the position of the flitch in order to make the desired adjustment.

Mechanical vibration is likewise an important problem in the operation of a mechanical slicer, because of the play between gears, cranks, pins and the like, which inherently is present or which develops with wearing of the parts during operation of the machine. Such vibration is productive of irregularities in the action of the knife and as a consequence the surface of theveneer cut is correspondingly rough and irregular.

The present invention is directed toward the solution of the foregoing and other problems, it being a general object of the invention to provide a veneer slicer which will produce veneer, particularly vertical grain veneers, suitable for use in the manufacture of structural plywood on a large commercial scale.

A further object is to provide a veneer slicer wherein the stroke of the cutting member is adjustable to accommodate fiitches of varying vertical dimensions.

A further object is to provide a veneer slicer having means for readily and easily adjusting the angle of cutting, or draw.

A further object is the provision of a veneer slicer the operating speed of which may easily be controlled within a relatively wide range.

A further object is the provision of a veneer slicer wherein are provided means for accurately stopping and sharply reversing the stroke of the cutting member at a precise and predetermined end point.

A further object is to provide a veneer slicer the knife of which moves at a constant velocity.

A further object is to provide a veneer slicer the output of which in square feet of veneer per unit time will be substantially constant even whenprocessing fiitches of Varying dimensions.

A further object is the provision of a veneer slicer the cutting member of which may be opera 3 ated at a constant cutting velocity which is the optimum velocity for wood of a given type and structure.

A further object is the provision of a slicer for making vertical grain veneers the production of which will be suificiently high to be suitedeconomically to use with the assembling, gluing, pressing and sanding operations of orthodox plywood manufacture.

A further object is to increase the productive efficiency of a veneer slicer by providing means for positioning the knife so that it can be sharpened without removal from the machine.

A further object is to enable the production on a large commercial scale of vertical grain veneer of high quality and uniform surface.

A further object is the provision of a machine for slicing veneers which is relatively free from mechanical vibration at high operating speeds.

A further object is to provide a machine of sufficient power and flexibility to be able to slice from a flitch veneers of substantial length, i. e. veneers having a length as great as sixteen feet or even more.

A further object is to provide a veneer slicer of such a design as to be operable upon flitches of small'cross sectional area.

A further object is the provision of a veneer slicer sufficiently versatile to be used in cutting woods of a wide variety of species of trees, in-

cluding many of those which, because of the physical structure of the wood, cannot be handled on a lathe-type machine.

A further object is to provide means in a veneer slicer for firmly positioning a battery of fiitches of varying heights and for urging them toward the mouth of the machine.

The operation of the herein disclosed hydraulic veneer slicer will be apparent from a consideration of the following specification and claims, taken together with the accompanying drawings wherein like numerals indicate like parts and wherein:

Figure 1 is a section taken along the cutting plane of a veneer slicer of the invention in one of its embodiments;

Figure 2 is an elevation, partly in section, looking toward the mouth of a veneer slicer of the invention in another of its-embodiments;

Figure 3 is a vertical section taken along the line 33 of Figure 2;

Figure 4 is a detail section showing in enlargement the knife and related members and the hold-down means, illustrated generally in Figure 3;

Figure 5 is another detail section illustrating an alternate method for attaching the knife to the frame of the slicer, whereby it may be swung clear of the frame to facilitate sharpening of the cutting edge withoutdetachment from the machine;

Figure 6 is a graph showing comparative velocity curves of hydraulic and crank actuated knives having the same stroke and maximum velocity; and

Figure 7 is a velocity curve for an hydraulically-actuated knife having a stroke approximately one-half the length of that of the knife of Figure 6.

' Considering the drawings in greater detail:

In Figure l, the frame of an hydraulic veneer slicer is indicated generally at I0, l0, l0. This may be made of welded plates, castings and structural members of sufficient'strength to support the moving parts of the assembly. It is provided with the stationary guide members of tracks H, H, which usually are in a vertical position.

Positioned within the stationary guide memhere on the frame are the slide members l2, l2. These are adapted to move freely within the guide members H, H and carry substantially at right angles the guide members, l3, l3, l3, 13. When the slicer is in a normal operating position, each of these assemblies comprises a vertical slide carrying a horizontal guide. They are actuated within the guides l I, i I by means of adjustable stroke hydraulic cylinders l4, l4 having an action which is synchronized so that they move together. Preferably, the hydraulic cylinders are double acting in order to obtain uniform cutting of the veneer. This overcomes any tendency of one end of the knife to move more rapidly through the wood than the other, and insures an even out being made.

Slidably positioned within the guides 13, I3 is a knife carriage or sash 16 to which is attached a cutting member or knife 17, a pressure bar l8 and, preferably, a wear plate IS. The pressure bar serves the function of pressing against the surface of the flitch just ahead of the knife so as to compress the wood slightly and enable the knife to make a straight, smooth, uniform cut. The gap between the knife and pressure bar serves as a passageway for. the sheet of veneer as it is cut and ejected from the machine.

Means for actuating the sash and the knife and other members which it carries are provided in the form of the adjustable stroke hydraulic rams 2i, 2|. These maybe single-acting and are synchronized so that while one pushes against the sash, the other is not exerting any pressure thereagainst and is being returned to its position of minimum displacement. As a result there is imparted to the sash a motion which is usually horizontal and which is substantially at right angles to the motion of the slide and guide assembly in which the sash is positioned.

In operation, the knife is made to approach and cut through a iiitch, represented in outline at 22, by causing a flow of oil to pass through the hydraulic cylinders l4, I4 and 2|, 2|. The oil flow is controlled by means of suitable valves so that in normal operation a vertical component is given to the sash by the action of the cylinders M, M while at the same time an horizontal component is imparted by-one or the other of the cylinders 21, 2!. The course followed by the knife is the resultant of the horizontal and vertical componentswhich thus determine the-cutting angle or draw of the knife. By a simple adjustment of the valves controlling the flow of oil to the hydraulic cylinders, the angle of draw readily may be varied to that which is best suited for use'on a flitch having a given grain structure.

Other features of the designand operation of the hydraulic slicer illustrated in Figure 1 are considered hereinbelow in conjunction with similar features of the alternate and preferred struc ture illustrated in Figures 2, 3, 4 and 5. In the latter structure, the frame of the slicer is indicated generally at 3? It'is fabricated from structural members, welded plates and castings and is so constructed as to provide a platform 3| havinga bar 32 of lead or other soft material positioned directly below the knife and designed to prevent drilling of the latter. Upon the platform are disposed a number of flitches 33, 33 which together comprise abattery whichmay be 48 inches or more 'in'depth. The flitches may be of varying vertical dimensionsfbut preferably are;

about 14 inches in height. Their length likewise is variable, the slicer being designed to accommodate flitches having a length of 16 feet or even more. Holding the flitches tightly together and urging them toward the mouth of the slicer are a pair of rams 34, 34 acting upon the crosshead 35 which conveniently may have the form of a structural steel channel beam. As illustrated, the rams comprise pneumatic cylinders, although alternate mechanisms such as hydraulic cylinders or mechanical feeding devices may be employed if desired.-

The flitch which is immediately adjacent the knife and which is being acted upon thereby is further held in position by a hold-down assembly which prevents its vertical displacement. The construction of this assembly is indicated in detail in Figure 4. In the embodiment illustrated, a spring member 36 contacts the upper surface of the flitch. The spring member may be in the form of a sheet of spring steel convexly curved with respect to the flitch and bent to form a skid section positioned farthest away from the knife and a raised section positioned near the knife. The skid section is so designed that as the flitches are pushed toward the knife their edges will not snag on the hold-down, but will be guided thereunder without difiiculty. The forward raised section forms with the top surface of the flitch a pocket adapted to receive a strip 3? of wood or other soft material. This extends forwardly of the spring member so that the forward surface is flush with that surface of the flitch which is to be cut. It is thus possible to exert pressure on the corner of the flitch which is contacted first by the knife without subjecting the latter to damage resulting from possible contact .with the hard substance of the spring member. Attachment of the strip 3'! to the spring member is secured by means of a series of bolts one of which,

is indicated at 38.

Positioned above the spring member and extending longitudinally thereof is the hold-down beam 39. This comprises a strip of steel or other strong material preferably having a longitudinal rib in the upper side thereof to impart to it the necessary strength and resistance to flexure. It is attached to the spring member by a series of bolts indicated at 4!. When suitably actuated, the hold-down beam serves the function of holding the spring member in a flexed position snugly against the upper surface of the flitch.

The desired actuation of the hold-down beam is secured by means of pneumatic cylinders 52, 42, preferably disposed one at either end of the beam and attached thereto through the rods 43, 53. Each of these extends through the beam and may be secured by means of a nut 44 with a washer 45. Thus when pneumatic pressure is applied to the cylinders in such a manner that the rod is retracted, the hold-down beam is drawn down toward the surface of the flitch and effects the flexure of the spring 36. This, in turn, holds the flitch snugly in place even though it is of a small or irregular size. It is to be noted that although other means may be employed for drawing and holding down the pressure bar, pneumatic means are especially well suited for this purpose since, due to the compressibility of air, the system is not rigid and yields slightly to permit advancing the flitches toward the knife. It is also possible easily and rapidly to vary the amount of pressure applied to the holddown beam, or to release it altogether when desirable or necessary to facilitate the advancement of the flitches toward the knife or the charging of the slicer with a new battery of flitches.

The knife assembly in this embodiment, like that in the embodiment illustrated in Figure l, essentially comprises a knife carriage or sash to which are attached a knife, pressure bar and wear plate. The sash 50 may have a size and shape adapted to the design of the machine, but may have on either end outwardly extending projections or arms 5|, 5| which extend substantially at right angles to the top surface of the sash. Located intermediately between these two arms is a third projection or driving member 52 which contacts the source of power by which the machine is operated.

The knife 53 is an elongated member which may be of varying dimensions depending upon the size of flitch tobe out. Its length may be, however, as much as 19 feet, or even more. Preferably, it has one concave surface and is provided with a cutting tip 54 made from a hard, wearresisting material such as high carbon steel. It is attached to the sash by means of a plurality of studs 55, 55, extending through holes in the sash and into the body of the knife. To enable adjustment of the position of the knife, the perforations in the sash through which the studs extend are sufficiently large to leave clearance between the side walls of the perforations and the shanks of the studs.

The pressure bar 56 serves the function of compressing the wood just ahead of the knife so that a clean cut is obtained. It is an elongated member of a length which is substantially equal to that of the knife. One edge of the bar is rounded or convexly curved. It is mounted on the sash below the knife in such a position that the rounded edge contacts and slides along a surface of the flitch ahead of the knife, so that the desired degree of compression of the wood is obtained during the cutting operation. Attachment of the pressure bar to the sash is obtained by means of a plurality of hold-down bolts or studs 51 positioned along the length of the bar, and extending through the body of the bar into the sash. Clearance is present between the walls of the perforations through the bar and the shanks of the bolts 57 to enable adjustment of the position of the bar.

As indicated above, the distance between the cutting edge of the knife and the edge of the pressure bar determines the thickness of the veneer 58 to be cut. Hence it is of importance to have present means for varying this distance and for maintaining it uniform along the entire length of the knife. In the form illustrated, the distance between knife and pressure bar may be varied by loosening the studs 55, 55, raising or lowering the knife until it is in the desired position, and then tightening the studs to hold it in place. In this manner, the gap may be varied to result in the production of veneers having a thickness which varies from a maximum of about -7 inch to a minimum of about 0.001 inch.

It will be apparent that slight irregularities may develop in the knife, either through wear with use or through the grinding operation by means of which a sharp cutting edge is maintained. Similar irregularities 'may develop in the edge of the pressure bar which cooperates with the knife. To compensate for this, and to insure that the gap between knife and pressure bar will be uniform along the entire length of the knife and. thus produce a veneer of uniform 7: thickness, means areprovided for-adjusting both pressure bar and knife and for warping them into desired positions. In the. form illustrated, such gitudinally of the pressurebar permits warping portions of the latter further to control and make uniform the gap between bar andv knife. Since the motion of the sash during. operation of the machine may drop the pressure bar 56-, the thrust bolts 81, BI, and a portion of the sash itself below the level of the frame 36, therelief 62 is present to prevent damage to the moving parts.

Also attached to the sash may be the wear plate 63. This comprises an elongated metal plate extending the length of the sash and so positioned as to be in frictional contact with a surface of the flitch. It preferably is detachable from the sash, being attached thereto by suitable means, as by means of'stud bolts-64, 64. It serves the function of protecting the body of the sash from wear by presenting to the flitch a smooth, renewable surface which may be replaced as it becomes rough or worn with use.

An alternate manner for attaching the knife to the sash is illustrated in Figure 5. In this embodiment, the knife 53 is attached through stud bolts 55, 55 to a holding member or knife head 10. The knife head, in turn, pivotally is attached to the sash through the bearing H and secured to the sash by means of the stud bolts l2, l2. Thrust bolts 60, 69 are also present in this embodiment for warping the knife to maintain a straight cutting edge, although in this case they extend through a portion of the knife head rather than through the sash itself.

This construction has the advantage that it enables sharpening of the knife without removal from the machine and consequent loss of production. After loosening the bolts 12, 72, the knife head with knife attached maybe swung clear of the sash and frame of the slicer into'the position indicated in dotted outline. In this position the knife edge may readily be sharpened, as by running a boner along the length of the blade.

In the event that it is desired to remove the knife from the slicer for any reason, as to grind it, the bolts l2, 12 may be loosened and the knife head detached from the bearings H. Since'the adjacent surfaces of the knife head and sash-may be'machined and knife heads made to a standard pattern, it is possible after removal of a knife head assembly from the slicer to replace it rapidly with another assembly, sharpened and adjustedand ready for use. This may beused while the knife which has been removed from the machine is being ground and adjusted. Shutdown time thereby is kept at a minimum, and 'the productive efficiency of the slicer is maintained at a high level.

The desired angular velocity is imparted to the sash and to the knife which it carries through means which are fundamentally similar to those used for giving the desired angularity of motion to the slicer illustrated in Figure 1. These comprise a slide member adapted to slide in a guide preferably built into the frame of the slicer and carrying a second guide member positioned substantially at right angles to that in the frame of the-machine and adapted to receive-as-a'second slide member. the knife-bearing sash, or an extensionthereof.

Thus, as isapparent from a consideration of Figure. 2, the fname'of the slicer has a guide 15 (corresponding to the guides 11, H of Figure 1). Sliding within this guide is a slide 16 (corresponding to the slides l2, 12 The slide 26 itself bears a guide formed integrally therewith and positioned substantially at right angles to the guide 15. This guide (i. e. the guide on slide 16') corresponds to the guides l3, l3, l3, 13 of Figure l. Slidingwithin the guide on the member 15, in amanner corresponding to that in which the sash l6 slides within the guides 13, I3, 13, i3, is the projection 52 of the sash 50. Just as it is possible by the application of suitably directed forces to the sash 1.6 of Figure l to impart to the sash vertical and. horizontal components of motion the resultant of which will be the desired angular motion, so it is possible by proper actuation of the projection "52 of the sash 55 of Figure 2 toi mparta similar angular motion thereto. In this manner a. desired and adjustable cutting angle, or draw, of the knife is obtained.

Actuation of the projection 52 and of the sash of which it is a part is obtained by attachment of the combination guide and slide member 16 as a crosshead tothe rod of a double-acting, adjustable stroke hydraulic ram 18. The ram is supplied with hydraulic fluid through the lines I9, 19 which, in turn, are fed with the variable displacement pump 80 driven by the motor 8|. It will be observed that the hydraulic ram, the

' pump and the motor are all mounted solidly on the frame of the slicer land-do not move with the action of the sash and knife. Furthermore, the lines necessary for transmitting fluid to various parts of the hydraulic system interconnect stationary parts. Thisis significant, since as a result they are not subject to fiexure and wear.

The cutting angle or draw of the knife is controlled by supporting the sash to which the knife is attached in the supporting members 85, which are attachedpivotally to the frame through the trunnion bearings 86, 86. Such support is obtained by pivotally attaching the projections 5|, 5| of the sash to slides 87, 81 which are adapted to slide within guides positioned on the support members 85, 85. These guides are maintained substantially parallel by means of an interconnecting rod 98 each end of which pivotally is attached to one of the support members through bearings 9|.

The angle of the guides in the support members 85, 85 is controlled by means of the worm gear and hand wheel assembly 92 which is attached atone end to anextremity of one of the support members through the bearing 93 and at the other to the frame of the slicer through the bearing 94. Rotation of the hand crank thus causes simultaneous pivoting of the guide members 85, '85 about the trunnion bearings 86, 86 so that the guide members conveniently may be adjusted toany desired angle. In ordinary operation, the cutting angle or draw thus obtainable varies between about 20 and about 70 from the vertical.

In operation, the double acting, adjustable stroke hydraulic ram"; is caused to reciprocate smoothly and. without vibration by pumping oil therethrough from the variable displacement pump 80. The crosshead I6 is thereby caused to slide back and forth in the crossheadguide 75. This exerts force upon the projection 52 of the sash which is caused to slide within the guide in the crosshead 16. The direction of motion of the sash and hence of the knife attached thereto is determined by the angle of setting of the support members 85, 85 to which the sash pivotally is attached through the sash slides 81, 81. The angle of motion may easily be changed by a simple adjustment of the worm gear and hand crank assembly 92. There thus is provided a simple but effective means for controlling the angle of cutting, i. e., the draw, to conform to the grain structure present in any given flitch.

The speed at which the slicer operates, expressed in number of strokes of the knife per unit time, also is subject to precise control. It may be controlled, for example, by increasing or decreasing through adjustment of the variable displacement pump 80 the quantity of hydraulic fluid pumped through the ram in a given time. The length of stroke and cutting angle being kept constant, the speed of the knife is directly proportional to the amount of fluid pumped through the ram per unit time. Further control of the cutting speed may be obtained by regulating the stroke of the ram. In this case the speed of the knife will be inversely proportional to the length of stroke, the velocity and cutting angle being maintained constant. Varying the cutting angle or draw likewise affects the speed of the knife, when speed is expressed as number of strokes per unit time. As the angle of the support members 85, 85 is increased away from the vertical, the cutting angle will be increased correspondingly, and the knife will have to travel a greater distance to cut through the flitch. Hence the speed of operation of the slicer will correspondingly be decreased. By controlling these various factors, the speed of the slicer may very accurately be controlled over a wide range of operating speeds, e. g. speeds varying between 0 and about 90 strokes per minute.

Not only is the speed of the slicer easily controlled and maintained, but the velocity of the knife during any given stroke may be kept constant throughout substantially the entire stroke. This effect is not obtainable with the mechanical slicers of the prior art, as readily is ascertainable from a consideration of Figures 6 and 7. These are velocity curves for hydraulic type and crank type slicers, wherein the displacement of the knife is plotted against the time. Curve AA is a curve for a hydraulic slicer, while curve 3-3 is a curve representing the motion of the orthodox crank-actuated slicer. It will be noted that the velocity of the crank-actuated machine is extremely variable. It is very high during a relatively short intermediate portion of each stroke and gradually decreases and then increases as the end point of each stroke is reached and passed. When such an action is applied to the cutting of wood, as in slicing veneer, it is apparent that the variable velocity of the cutting stroke will be reflected in the quality of the veneer cut. .Portions of the veneer surface which are out while the knife is moving at optimum cutting velocity will be of satisfactory quality; other portions out while the knife is travelling too rapidly or too slowly will be rough and uneven.

Furthermore, the time elapsing during deceleration and acceleration of the knife is very substantial in the case of the crank-driven slicer. In curve B-B this time is indicated by the distance between lines bb. This likewise is significant and is reflected in the nature of the cut made through the flitch. Since the velocity is 10 very low at the end of the stroke, the result will be that the fibers are torn apart rather than severed during this portion of the stroke so that a clean cut is not obtained. If it is sought to avoid this effect by permitting the knife to overcarry a substantial distance beyond the plane of the flitch, so that only the maximum velocity of the stroke is utilized, it will be apparent that the productive capacity of the slicer in square feet of veneer cut per unit time will be reduced correspondingly.

In contrast to the foregoing, it is evident from an inspection of the curve AA for the hydraulically actuated slicer that the velocity of the knife remains constant over substantially the entire stroke. Just as an irregular cutting stroke produces a non-uniform and irregular surface in the veneer cut, so a stroke made at uniform velocity produces a veneer having a smooth and regular surface. Furthermore, as noted above, by controlling the variable displacement pump which supplies fluid to the hydraulic cylinder, the velocity readily may be maintained at an optimum value. Hence the hydraulic actuation of a slicer knife has a material and significant effect on the quality of the veneer produced.

It will further be apparent that the reversal of the knife in a hydraulic slicer is practically instantaneous. The time elapsing during reversal, represented by the distance between the extension lines a-a of curve A-A, is of the order of from to second. During this time the distance the knife travels is but very little. It amounts usually only to the amount of overrun into the lead bar positioned in the frame below the knife. As a result, high velocity is maintained until every fiber of wood binding the veneer to the flitch has been severed, and the terminal portions of the out are as smooth as are the intermediate portions. This likewise materially affects the quality of the veneer produced. It is noteworthy that such sharp reversal is peculiar to the action of hydraulically driven knives, as compared with those driven by compressed air or steam. In the case of the latter, the medium through which the power is transmitted is compressible, and sharp reversal of direction of stroke is therefore impossible.

Not only is it possible significantly to improve the quality of veneers by application of hydraulic power to a veneer slicer, but it also is possible to increase very materially the quantity of veneer cut by a given machine in unit time. This comes about as a result of two factors. In the first place, since the velocity of the knifeis maintained constant at a relatively high rate of speed, and since the time elapsing during reversal of direction is insignificant, the knife of an hydraulic slicer completes more cycles in a given time than does the knife of a mechanical slicer having the same maximum velocity. This is apparent from inspection of the curves AA and B-B of Figure 6. In both cases the maximum velocity, as indicated by the slope of the intermediate portions of the curves, is the same. However, in the time indicated in the curves, the hydraulic slicer has completed 4 complete cycles or oscillations, while in the same time the mechanical slicer has completed but 1 /2.

A second factor tending materially to increase the yield of veneer obtainable from an hydraulic slicer over that obtainable from a mechanical slicer operating at the same maximum velocity results from the fact that it is not possible to change the length of stroke of a mechanical slicer without taking down the machine and re,-

building it. Hence, where the vertical dimension of the hitch isreduced sothat it is materially lessthan theleng-th of-stroke of the slicer, there is-considerable overrun of the knife with con sequent loss of production. Although the number ofsli'ces produced per unit time will be the same when=smaller flitches are cut, the area of each slice'will be decreased correspondingly so that the production of the machine in square feet of veneer cut per unit time will be decreased.

'ofthe-ram, the velocityof the knife will be maintained constant. If the stroke of the knife is -made less-while the velocity is maintained constant, the number of strokes per unit time will correspondingly be increased so that the number of square'feet of veneer cut will remain constant.

If, as illustrated by the curve C-C of Figure 7 considered togetherwith the curve A-A of Figure 6, the stroke of theknife is reduced to a value which is but one-half the original stroke, the velocity" being kept constant, in a given timethe knife having the shorter stroke Will out almost twice as many slices as that having the longer stroke withthe result that the number of square feet ofveneerproduced will be the same. Hence it is' possible by the application of hydraulic actuation to a veneer slicer in the manner described herein to achieve not only operation at a constant, optimum velocity to produce a high quality product at high production rates, but it is *also possible to produce veneer at maximum cutting efficiency and at a constant output.

Having now described our invention, what we claim as new and desire to protect by Letters Patent is:

1-. A machine for slicing veneers from blocks of wood which comprises a-supporting structure, a knife carriage slidably positioned on said supp'orting structure, a knife attached to said knife carriage, hydraulicmeans for reciprocally actuating said knife carriage, and means for adjusting the draw of said knife carriage, said means comprising a first guide member on said supporting structure, a first slide member adapted to slide in said first guide member, a second guide member attached to said first slide member and positioned substantially at right angles to said first guide member, said second guide member being adapted to receive as a slide member said knife carriage.

'2. In a veneer slicer comprising a frame, a sash slidably mounted on said frame, a knife attached to said sash, and means for actuating said sash; means for controlling the angular motion of said sash and comprising a first guide means on said frame, a first slide means adapted to slide in said first guide means, and a second guidemeans attached to said first slide means, said second guide means being adapted to receive said sash asa slide.

3. A veneer slicer comprising a supporting structure, a knife carriage, a knife attached to said knife carriage, first guide members on said supporting structure, first slide members adapted to move in said first guide members, second guide members positioned on said first slide members and adapted to receive as a secondslide member said knife. .carriage, and hydraulic means attached to said first slide members and to said knife carriage to' secure the reciprocal actuation thereof.

4. The veneer slicer of claim 3 wherein said hydraulic means comprises hydraulic rams attached to said first slide members and to said knife carriage.

5. A veneer slicercomprising a frame, a sash, a knife attached to said sash, a pair of first guide members on said frame, a pair of first slide members adapted to move in said first guide members, a pair of second guide members positioned on said first slide members substantially at right angles to said first guide members and adapted to accommodate said sash: slidably mounted therein, a first pair of hydraulic rams attached oneto each of said first slide members, and a second pairof hydraulic rams acting against opposite sides of said sash and having a motion which is directed substantially at right angles to the motion of said first pair of hydraulic rams.

'6. A veneer slicer comprising a frame, a sash having a projection extending from one side thereof, a knife attached to said sash, a guide on said frame, a-slide adapted to move in said guide, another guide on said slide, said another guide being adapted to receive as another slide said projection on said'sash, means for slidably attaching said sash to said frame, and hydraulic means for effecting the reciprocation of said slide in said guide.

7. A veneer slicer comprising a frame, a sash having a projection extending from one edge thereof, a knife attached to said sash, a guide on said frame, a slide adapted to move in said guide, a guide positioned on said slide and adapted to receive as a slide said projection on said sash, guide members pivotally attached to said frame, slide members positioned within said guide members, means for pivotally attaching said sash to said slide members, and hydraulic means for reciprocating said slide within said guide on said frame.

8. A veneer slicer comprising a frame, a sash having a projection extending from one edge thereof, a knife attached to said sash, a guide on said frame, a slide adapted to move in said guide,

REFERENCES CITED The following references are of record in the file of'this patent:

UNITED STATES PATENTS Number Name Date 654,635 Hindleyet al. July 31, 1900 1,051,381 Berry Jan. 28, 1913 1,121,707 Zimmerman et al. Dec. 22, 1914 1,143,081 Shellenberger June 15, 1915 1,226,185 Carlin May 15, 1917 1,339,051 Barrett May 4, 1920 1,515,013 Costa Nov. 11, 1924 1,815,670 Haworth July 21, 1931 2,400,996 'Iversen May 28, 1946 

